Nuclear reactors are shut down by the insertion of rods containing poisons for parasitic neutron absorption. Rod drives are typically connected by drivelines to the rods.
A first form of rod driveline includes a mechanical connection, typically threaded, between the driveline and rod. A second type of driveline includes a driveline which can selectively attach and release a rod. This disclosure relates to this second type of driveline.
Rod release mechanism from drivelines are known. Moreover, thermally responsive rod release mechanisms are known. A common type of thermally responsive rod release mechanisms includes an electromagnetic coupling between the mechanism and a magnet. When the magnetic portion of the rod adjacent a magnet reaches the Curie point of the metal and becomes non-magnetic, rod release and drop occurs.
Rod excursion responsive to reactor overheat is known. See Zebroski U.S. Pat. No. 4,227,967. In this type of device, concentric cylinders of bimetallic differential expansion properties are series connected for maximum thermal excursion. When the reactor is too hot, rod insertion occurs. When the reactor cools and rod drive movement has occurred, rod withdrawal occurs.